1. Field of the Invention
The present invention relates to a noise reduction apparatus adapted to reduce noise in a video signal using a pseudo noise signal generated according to a signal which may be a noise source and an image pickup apparatus provided with the noise reduction apparatus.
2. Description of the Related Art
For example, in a video camera, there has been proposed a noise reduction apparatus adapted to reduce a periodic mechanical noise generated by a recording tape contacting a rotary magnetic head (for example, Japanese Laid-Open Patent Publication (Kokai) No. 2003-317409).
The above conventional noise reduction apparatus is described below.
The conventional noise reduction apparatus mainly includes an adaptive signal processing circuit and a pseudo noise subtracter. The adaptive signal processing circuit receives a reference input pulse signal synchronized with a noise signal to be reduced to produce a pseudo noise signal which is approximate to the noise signal to be reduced.
The pseudo noise subtracter subtracts the pseudo noise signal from a main input signal on which the noise signal to be reduced is superimposed and feeds the difference back to the adaptive signal processing circuit to update the adaptive signal processing circuit to minimize the noise power of a subtraction output.
Thus, the conventional noise reduction apparatus feeds the output of the pseudo noise subtracter back to the adaptive signal processing circuit to cause the adaptive signal processing circuit to learn a noise characteristic by using an adaptive signal processing. This probably causes overcorrection in which the main signal component that is highly correlative to a signal of a noise-source is erroneously detected as a noise and subtracted.